Epicycic geartrain, a gearbox, and aircraft, and a method

Abstract

An epicyclic gear train including a plurality of planet gears that are carried by a common planet carrier, the planet carrier comprising a support and a plurality of pins carried by the support, each pin having a fastening segment extending in a direction away from the support to a distal end, each planet gear being arranged around a respective one of the fastening segments and presenting a degree of freedom to move in rotation about an extension axis along which the fastening segment extends. A retaining link is carried by the pins and connects the pins together, each planet gear being arranged in a zone lying between the support and the retaining link, each pin presenting a restricted degree of freedom to move relative to the retaining link.

What is claimed is: 
     
       1. An epicyclic geartrain comprising a sun gear and an outer annulus gear, the epicyclic geartrain being provided with a plurality of planet gears that are carried by a common planet carrier, the planet carrier comprising a support and a plurality of pins carried by the support, each pin having a fastening segment extending in a direction away from the support to a distal end, each planet gear being arranged around a respective one of the fastening segments and presenting a degree of freedom to move in rotation about an extension axis along which the fastening segment extends, wherein the epicyclic geartrain includes a retaining link that is carried by the pins and that connects the pins together, each planet gear being arranged in a zone lying between the support and the retaining link, each pin presenting a restricted degree of freedom to move relative to the retaining link, the retaining link including a respective centering stud for each pin, each pin and an associated centering stud being engaged at least in part axially one in the other along the extension axis of the pin, the centering stud penetrating into a cavity in the associated pin or the pin penetrating into a cavity in the associated centering stud, a pin and the associated centering stud being spaced apart at rest by radial clearance perpendicular to the extension axis of the pin. 
     
     
       2. The epicyclic geartrain according to  claim 1 , wherein the retaining link comprises a plate. 
     
     
       3. The epicyclic geartrain according to  claim 1 , wherein the retaining link is annular in shape. 
     
     
       4. The epicyclic gear rain according to  claim 1 , wherein each centering stud includes a connection wall, each pin including a web, and each connection wall is screwed to a web by a threaded member. 
     
     
       5. The epicyclic geartrain according to  claim 4 , wherein, at rest, the connection wall bears along the extension axis against the web. 
     
     
       6. The epicyclic geartrain according to  claim 4 , wherein the threaded member and the web are spaced apart radially by first clearance perpendicular to the extension axis of the pin, the threaded member and the connection wall being spaced apart radially by second clearance perpendicular to the extension axis of the pin, at least one of the first clearance and the second clearance being greater than the radial clearance. 
     
     
       7. The epicyclic geartrain according to  claim 6 , wherein at least one of the first clearance and the second clearance is greater than or equal to twice the radial clearance. 
     
     
       8. The epicyclic geartrain according to  claim 4 , wherein each pin presents an internal space in hydraulic communication with an outside medium, the pin presenting a lubrication orifice in fluid flow communication with a planet gear carried by the pin, the web presenting a first channel facing a second channel of the connection will, the second channel opening out to the outside medium. 
     
     
       9. The epicyclic geartrain according to  claim 4 , wherein the retaining link includes a stop system for stopping rotation of an inner race of a bearing member of each pin, the stop system projecting from the retaining link towards the zone in order to prevent the inner race of a bearing member from rotating relative to the pin, the bearing member being interposed between a pin and a planet gear. 
     
     
       10. The epicyclic geartrain according to  claim 1 , wherein between two centering studs, the retaining link presents thickness that is at least five times smaller than the thickness of the support. 
     
     
       11. A gearbox wherein the gearbox includes the epicyclic geartrain according to  claim 1 . 
     
     
       12. An aircraft wherein the gearbox includes the epicyclic geartrain according to  claim 1 . 
     
     
       13. A method of optimizing the epicyclic geartrain comprising a sun gear and an outer annulus gear, the epicyclic geartrain being provided with a plurality of planet gears that are carried by a common planet carrier, the planet carrier comprising a support and a plurality of pins carried by the support, each pin having a fastening segment extending in a direction away from the support to a distal end, each planet gear being arranged around a respective one of the fastening segments and presenting a degree of freedom to move in rotation about the fastening segment extends, wherein each distal end is spaced apart from another distal end adjacent thereto by a distance, and the method including a step of connecting the pins together with a retaining link, each pin having a restricted degree of freedom to move relative to the retaining link, the retaining link exerting no force on the pins under normal conditions, and keeping the distance within a predefined range in the presence of a crack in a planet gear, the retaining link including a respective centering stud for each pin, each pin and an associated centering stud being engaged at least in part axially one in the other along the extension axis of the pin, the centering stud penetrating into a cavity in the associated pin or the pin penetrating into a cavity in the associated centering stud, a pin and the associated centering stud being spaced apart at rest by radial clearance perpendicular to the extension axis of the pin.